The present invention relates to printing devices and systems. More particularly, the present invention relates to method of and detector for distinguishing different transparency media types for a printer.
Overhead projection devices commonly use printed transparent films or sheets (xe2x80x9ctransparenciesxe2x80x9d) to project information onto a projection screen. The transparencies are often printed using laser printers or inkjet printers. However, different types of transparencies are used for the different type of printers. This is because the laser printers and the inkjet printers use different techniques and materials for the print operation, thus requiring different properties from the transparency media.
Laser printers electrostatically deposit toner on a medium, and then fuse the toner onto the medium by applying pressure and heat to the medium having the toner deposits. The pressure and the heat are applied using a fuser. The fuser may reach temperatures of 150 degrees Celsius or more. Because the toner is electrostatically deposited and pressure-heat fused, a first type of transparencies (xe2x80x9claser transparenciesxe2x80x9d) are typically made of clear plastic (such as MYLAR(copyright)) substrate having smooth printing surface.
Inkjet printers require a different type of transparencies (xe2x80x9cinkjet transparenciesxe2x80x9d) because no fuser is used. The inkjet printer shoots tiny drops of ink onto the medium. The medium receives and retains the ink. Accordingly, an inkjet transparency includes an ink-receptive surface layer (such as gelatin or other materials) coated on a clear plastic substrate.
Although an inkjet transparency may have a rougher surface than surfaces of a laser transparency, the two types of transparencies are often difficult to distinguish. Further, many people are not even aware that an inkjet transparency should not be fed into certain types of laser printers. This is because the ink-receptive surface layer of the inkjet transparency melts from the fuser""s heat and sticks to the fuser. This requires a replacement of the fuser, which is a relatively expensive portion of the laser printer.
Accordingly, there is a need for a method and apparatus to recognize or prevent the feeding of inkjet transparencies into a laser printer.
These needs are met by the present invention. According to a first aspect of the present invention, a printer has a transparency film discrimination system including a feed mechanism for feeding a print medium toward a print mechanisms, the print medium being one of a plurality of different types, each type having a print surface. The printer also includes an illumination source for providing light to impinge on the print surface and a detector for detecting one of reflected and transmitted light from the print surface to provide a detection signal representing the print surface so as to allow identification of transparency type of the print medium. Further, the printer has a processor for applying metric criteria to the detected signal to identify type of transparency of the print medium and for providing control to the print mechanism dependent on the identified transparency type so that damage to the printer is avoided.
According to a second aspect of the invention, a method of operating a printer is disclosed. First, a print medium is fed toward a print mechanism, the print medium being one of a plurality of different types, each type having a print surface. Then, the print surface of the print medium is illuminated. Next, one of reflected and transmitted light from the print surface is detected to provide a detection signal representing the print surface so as to allow identification of transparency type of the print medium. Finally, metric criteria are applied to the detected signal to identify type of transparency of the print medium and for providing control to the print mechanism dependent on the identified transparency type so that damage to the printer is avoided.
According to a third aspect of the invention, a printer having a transparency film discrimination system is disclosed. The printer has a feed mechanism for feeding, to a print mechanism, a transparency film medium having a print surface and a first illumination source for providing light to transmit through the print medium. Moreover, the printer includes a detector for detecting the transmitted light for providing a detection signal to a processor. The processor is connected to the detector and to the feed mechanism and is programmed to apply a metric criteria to the detected signal to determine whether the print medium is of an acceptable type, and to signal the feed mechanism to reject print media of unacceptable type to prevent damage to the print mechanism.
Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.